Mapleson Circuits

Question 1

Mapleson A Magill

Answer 1

Good for spontaneous ventilation.
Controlled ventilation requires high flows.
APL at the patient end.
FGF builds up in reservoir bag and patient tubing.
When patient exhaled, pressure builds up in tubing causing APL to open releasing expired gas and some fresh gas.

Question 2

Mapleson A Lack

Answer 2

Good for spontaneous breathing.
Not suitable for controlled ventilation.
There is a co-axial system.
Internal tube larger diameter to decrease resistance for expired gas.
APL not at patient end so decreases drag.
Reservoir bag at machine.

Question 3

Mapleson B

Answer 3

Not good for spontaneous ventilation as high FGF are required to prevent re-breathing.
Good for controlled ventilation as corrugated tubing also acts as a reservoir.
FGF added close to APL.
APL at patient end.

Question 4

Mapleson C

Answer 4

APL at patient end.
Not good for spontaneous ventilation as high FGF are required to prevent re-breathing.
FGF added just before APL.

Question 5

Mapleson D (Bain)

Answer 5

Spontaneous ventilation requires high gas flows.
Controlled ventilation more efficient.
Can remove reservoir bag and connect to ventilator using corrugated tubing.
Co-axial system.
Reservoir bag machine end.
APL machine end.
Expired gas through outer tubing, inspired gas through inner tubing.
Internal tube has swivel mount to prevent kinking.
Exhaled gas goes back to reservoir bag and builds pressure opening valve.

Question 6

Pethicks test (on Bain circuit)

Answer 6

This test is for the Bain circuit as occlusion or disconnection of inner FGF tubing is a hazard in this circuit.
Occlude patients end.
Close APL.
Fill circuit with oxygen flush.
Release occluded end and flush, bag should flatten due to venturi effect if inner tube is patent.

Question 7

Mapleson E

Answer 7

Valveless system.
No bag on end of ciruit.
Can use thumb to occlude the end instead.
Requires high FGF greater than 4-6L/min to prevent re-breathing.

Question 8

Mapleson F (Jackson-Rees Modification)

Answer 8

Valveless system good for spontaneous or controlled ventilation.
Volume of tubing indicates amount of re-breathing should be approximately the patients tidal volume.
Requires high FGF greater than 4-6L/min to prevent re-breathing.
No scavenging.